The present invention relates to a storage system and a data management device for a storage system.
The storage system is constituted by comprising at least one or more storage device, known as a disk array sub-system, for example. This storage device provides a storage region based on a RAID (Redundant Arrays of Inexpensive Disks) system, wherein disk drives, such as hard disk drives, semiconductor memory devices, or the like, are arranged in an array configuration. A host computer (hereinafter, called “host”) accesses the logical storage region provided by the storage device and reads or writes data.
The volume of data managed by businesses and organizations such as regional authorities, educational institutions, financial institutions, government and municipal offices, and the like, is growing steadily year on year, and some of this data is designated by the law or other regulations as data that must be kept in store for a prescribed number of years. Therefore, the system administrator selects the data that is to be stored, from the group of data accumulated in the storage system, and he or she backs up that data. One method for backing up data is known wherein a plurality of copy destination volumes of the same size of the copy source volume are prepared, for example, and data for respective generations is stored respectively in these respective copy destination volumes (Japanese Patent Laid-open No. 2004-046435).
In the patent referenced above, since an identical copy of the whole of the volume is saved, regardless of the size of the data that is to be saved, then the use efficiency of the storage region declines. Specifically, data of a prescribed size is generally saved by writing it to a storage medium of a fixed size, and therefore, in a storage system, a plurality of volumes of a fixed capacity are prepared and data is saved by writing it to these fixed-size volumes.
However, the size of the data to be backed up varies on a daily basis, depending on the frequency of use of the application programs, and the like. Therefore, it is necessary previously to set the size of the volume for saving data to a larger size than the data that is to be backed up. The size of the volume for saving data is established on the basis of past experience, for example. In this way, since a data saving volume is prepared in advance to a size that is larger than the predicted size of the data to be backed up, then wasted empty capacity is generated in the data saving volume and the use efficiency of the storage region declines. Moreover, since it is hard to predict the size of the data saving volume accurately in advance, then it is difficult to use the storage resources efficiently in the overall storage system.